1. Place order for items that you want to purchase
2. Set payment type to proforma and finalize the order
3. Once you receive confirmation e-mail DO NOT make payment yet.
4. E-mail me order number (just reply to order confirmation) and ask for shipping type to be changed to regular mail
5. We will manually change shipping type for you and e-mail you corrected proforma
6. You will now be able to pay via bank transfer and enjoy cheaper regular air mail.

Note air mail is not ensured nor trackable and in ~1% of cases it does get lost. You take the risk which is also why you can't get this shipping type with other payment types.